Some industrial machines (e.g., locomotives, trucks, earth-moving equipment, windmills, and the like) include assemblies (e.g., mechanical drive trains) that operate within environments such that they endure one or more of thermal stress, torsional stress, and shock and vibration. It may be desirable to monitor a condition of an assembly so that the assembly may be replaced or repaired before severe or permanent damage is sustained.
Sometimes, fluid lubricants may provide lubrication and cooling to increase performance of the machine and/or to increase the lifetime operation of the machine. In one example, speed control from a traction motor or other provider of mechanical power may be accomplished with a gear train or drive train. Gear trains may include at least two gears that engage each other. For instance, teeth of a first gear (e.g., pinion gear) may engage teeth of a larger gear at a gear mesh. Gears may be lubricated by a lubricant (e.g., oil) to reduce the friction between the gears and to facilitate the dissipation of heat that is generated during operation. In order for the gears to be suitably lubricated, a designated amount of lubricant is available for use by the gears.
A gear train may include a gear case that surrounds one or more parts of the gear train. The gear case has a reservoir for holding the lubricant. At least one of the gears may move through the reservoir to lubricate the gear and consequently the gear mesh. At least one of the gears may be coupled to a shaft that projects out of the gear case. To prevent leakage from the reservoir or the gear case, the interface between the shaft(s) and the gear case is sealed. In one embodiment the gear train may include a U tube coupled to the axle, and may have a reservoir for grease.
The sealed interfaces may be exposed to harsh conditions. For example, gear trains may be exposed to large differences in temperature, humid environments, dry environments, abrasive dirt or grime, and/or challenging vibratory states. These conditions may cause a failure in the sealed interface thereby resulting in leakage of the lubricant. When an insufficient supply of lubricant is available for the gears, the machine may be susceptible to gear train or rolling element bearing damage that results in a locked axle condition.
In addition to having a sufficient amount of lubricant, it may be desirable for the lubricant to have a sufficient quality during operation. For example, lubricants in a reservoir can become contaminated by water, metallic particles, and non-metallic particles. Contaminated fluids may lead to damaged parts or a decreased performance of the machine. In addition, the lubricant may age due to repetitive thermal and viscous cycles resulting in the loss of fluid properties such as viscosity.
Conventional methods of inspecting fluids of a machine include visual inspection of the fluid (e.g., dipsticks) or a sensor that is directly wired to a system. However, these methods may not be practical and/or may have limited capabilities. For example, due to the configuration of some machines, it may be difficult to visually inspect the fluid. Also, hardwired sensors may not be suitable for machines that frequently move and/or are exposed to harsh conditions.
Battery life is a concern for wireless devices that are, for example, difficult to access. Larger batteries may have longer life, but may not be suitable for applications that have space constraints. Limitations on the capabilities of various sensors have restricted their use. These limitations may include thermal resistance and current draw. Naturally, the amount of current a sensor uses may not be as relevant if power can be supplied by a wire, but in wireless systems the amount of current draw may prohibit sensors from use entirely. Additionally, the thermal capabilities for some sensors have precluded their consideration for many applications. Accordingly, existing sensing devices often, if not always, use a low temperature sensor with low power combination, particularly for wireless sensing applications. Conversely, low and high temperature sensors with high power combinations have been available for wired power applications.
It may be desirable to have a system and method for inspecting machines that differs from those that are currently available.